In U.S. Pat. No. 4,008,775, issued Feb. 22, 1977, there is described a process in which porous iron oxide particles are used in drilling muds, primarily aqueous drilling muds, to scavenge hydrogen sulfide (H.sub.2 S) released from a well in the course of a drilling operation. This iron oxide is described as having an ideal composition of substantially Fe.sub.3 O.sub.4, a particle size of about 1.5 to 60 microns and a surface area at least ten times as great as magnetite particles of equal size.
In co-pending application Ser. No. 44,026, filed May 31, 1979, assigned to the same assignee as the present application, the iron oxide (referred to as Compound A), described in the aforesaid patent, is further characterized as having an amorphous (non-crystalline) moiety of Fe.sub.2 O.sub.3 together with an Fe.sub.3 O.sub.4 crystalline phase. Further, in said application other non-oxide particles (referred to as Compounds B and C) are described; specifically, iron oxide waste dusts from open hearth or basic oxygen furnace steel-making operations, are somewhat similar to the iron oxide particles of said patent in that they have large surface areas and have an amorphous moiety of Fe.sub.2 O.sub.3, and an Fe.sub.3 O.sub.4 and Fe.sub.2 O.sub.3 crystalline phase. Still another iron oxide composition (referred to as Compound D) having a high surface area and an amorphous Fe.sub.2 O.sub.3 moiety and a crystalline Fe.sub.2 O.sub.3 phase is described in said application. In said application it is also described that the aforesaid iron oxide particles are useful in scavenging H.sub.2 S from hydrocarbon gases by bubbling such gases through a water suspension of such iron oxide particles. The description in said co-pending application relevant to Compounds AD is hereby incorporated herein by reference.
U.S. Pat. No. 4,089,809, issued May 16, 1978, discloses that H.sub.2 S can be removed from producer gas by passing the gas (at very high temperatures) through a bed of pellets composed of silica and Fe.sub.2 O.sub.3 thereby forming the crystalline reaction products FeS and FeS.sub.2. This process is designed to remove H.sub.2 S from the producer gas immediately after such gas if formed and, as noted, at high temperatures of the order of 1000.degree.-1800.degree. C., which is considerably higher than that of most gases, e.g. natural gas containing H.sub.2 S.
U.S. Pat. No. 4,201,751, issued May 6, 1980, describes a process of reducing the H.sub.2 S content of noxious gases containing same by passing the gas through a bed of perlite, an alkaline agent and iron III-oxide in the form of dust developed during production of iron or steel. The reaction products formed are not specified and the process appears to be directed primarily to the use of alkaline agents and the treatment of gases at elevated temperatures.
My present invention does not require such extremely high temperatures. It is a process for scavenging H.sub.2 S from gases using certain iron oxide particles which react with the H.sub.2 S to form reaction products which for the most part are not crystalline, but are substantially amorphous; however, they are stable, and do not release significant quantities of H.sub.2 S on contact with air.